Production of artificial filaments and similar products from cellulose xanthogenates



Patented Dec. 9, 1952 PRODUCTION OF ARTIFICIAL FILAMENTS AND SIMILAR PRODUCTS FROM CELLU- LOSE XANTHOGENATES Nicolas Drisch, Paris, France, assignor, by mesne assignments, to Textile and Chemical Research Company Limited, St. Peter, Port of Guernsey, Channel Islands, a corporation of Great Britain No Drawing. Application February 16, 1951, Se-

rial No. 211,427. In Great Britain August 11,

11 Claims.

This invention relates to the production of artificial filaments and similar products from cellulose xanthogenates and particularly to the production of filaments from such materials by a dry-spinning process.

For the production of artificial filaments using cellulose xanthogenate it is customary to employ that material in the form of its fully hydrated dispersion in aqueous caustic soda, such dispersion commonly being called viscose.

It is known to dry-spin viscose and apparatus has been described similar to that known for the manufacture of artificial yarns from solutions of cellulose derivatives in organic solvents, i. e. a column in which a spinneret is provided at the top, the viscose being extruded through the spinneret to form a bundle of filaments which in their passage down the column are coagulated by partial evaporation of the solvent medium by a current of hot gas, for example air or carbon dioxide. The evaporation of the Water from the extruded viscose filaments can be accelerated by maintaining a partial vacuum in the column. In the dryspinning of viscose under these conditions it is also known to use concentrated solutions, for example Viscoses containing 16% of cellulose. Further, it is known that the spinning properties of the viscose in the dry-spinning process, can be substantially improved by an addition to the viscose of certain derivatives of antimony.

It has now been found that it is possible to convert aqueous dispersions of cellulose xanthogenate into filaments without supplying external heat and without the necessity of exerting a physical or chemical action on the solution as soon as it leaves the spinnerets.

According to the present invention a process for the production of filaments and similar products from cellulose xanthogenate comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda which has a viscosity of at least 1000 poises, and which has a cellulose content of at least 6%, and a caustic soda content of 3 to the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products by treatment with cold dilute acid or hot aqueous liquid of pH at least 7.

Such dispersions are hereinafter referred to as xanthogels and, more particularly, the xanthogel must satisfy two conditions:

cellulose content may vary from 6 to 25% according to the degree of depolymerisation of the cellulose. The new expression xanthogel has been coined to distinguish from viscose by which is meant dispersions in which the volume of the dispersing phase (Water plus caustic soda) is sulficient to produce total hydration of the molecules in small groups of dispersed molecules. In the xanthogel, on the other hand, the volume of the dispersing phase is insufficient to produce total hydration, which gives very great internal cohesion.

2. The internal molecular dispersion must be as uniform as possible. The direct preparation of xanthogenate gels by the known means does not produce such dispersion. In fact, the insufficiency of the dispersing phase under normal conditions of dissolution leads to the formation of pastes containing large micellary aggregates of low degree of hydration, the degree of hydration being extremely heterogeneous. It is therefore necessary to use special means to obtain such gels. These gels can be obtained by treating normal viscoses with an organic solvent which is miscible with water but does not dissolve the cellulose xanthogenate, e. g. acetone or pyridine. The addition of the solvent produces a separation into two layers, namely solvent diluted with water and viscose of low water content, the consistency and composition of which vary as a function of the quantity of solvent employed.

It has also been found that homogeneous gels can be obtained by combining a powerful mechanical dispersion with a rapid swelling at low temperature. The most convenient method is to malaxate under high pressure a sheet of xanthate containing all the soda required, the rolls being cooled below 10 C., and to effect a number of successive passes While progressively adding increasing quantities of water, until the required composition is reached.

Under these conditions, gels containing 6, 10, 20 up to 25% of cellulose may be obtained, microscopic examination of which does not reveal the presence of any swelled but non-dispersed fibres. Moreover, the low temperature prevents hydrolysis of the fixed xanthogenate groups and the lowering of the 7 value during the preparation is only of the order of a few units. In order to obtain such dispersions. it is necessary to use xanthogenate prepared from quantities of carbon disulphide higher than 35% and preferably from 40 to The 7 value is the number of 3 molecules of CS2 fixed as dithiocarbonate ester by 100 glucose units.

The xanthogel is extruded through the spinneret and the extruded filaments are led directly towards a winding device, a substantial stretching of the filaments being effected during this passage. It is surprisingly found that the internal cohesion of the Xanthogel is such that the extruded filaments do not break under this treatment and that the orientation imparted to the xanthogenate molecules by passage through the orifices of the spinneret (which preferably have considerable length e. g. 0.3 mm. or more), and by the subsequent stretching affords a setting of the filaments such that they can be handled on guide rollers as a composite thread without the filaments sticking together. It is thus possible, to effect the regeneration of the cellulose in the filaments while maintaining the individuality of. the filaments of the thread.

The thread obtained may be fixed and purified by treatment with a hot aqueous solution, such as water at 80-90 C., or With a hot saline solution. Xanthogels containing more than 10% and preferably more than 20% of cellulose, and having the required viscosity, have excellent spinning properties and the filaments can undergo stretching of several hundred per cent, e. g. 500 to 1000%, on leaving the spinnerets. Additional stretching may be carried out during the fixing treatment. Filaments of 0.3 denier and even substantially less, can be obtained by means of such high de gree of stretching, with ordinary spinnerets having holes of the order of 50 to 80 a. The final spinning speed may be very high, ior example up to 500 m./'min.

The invention is illustrated by the following examples which, however, are not to be regarded as limiting the invention in any Way:

Example I A normal viscose containing 6.5% of cellulose and 7% of caustic soda is mixed progressively with an equal volume of anhydrous acetone after intimate stirring, the mixture is decanted. The mixture separates into an upper layer of dilute acetone containing part of the caustic soda, carbon disulphide and sulphuretted impurities emanating from the xanthogenation reaction,

and a lower layer of concentrated viscose containing 15% of cellulose with 8.55% Of caustic soda. This concentrated viscose is degassed by the usual method. The last traces of acetone are dilficult to eliminate but they do not appear to be harmful. The viscosity is 4,500 poises. This viscose is dry spun at room temperature, with a spinneret having holes of 60 diameter, and, on application of a stretch of 300% by rollers, it is possible to obtain, for a suitable delivery under pressure of -12 kg./sq. cm. at the spinneret, iilaments of 0.3 denier. The set thread can be fixed by treatment with dilute sulphuric acid at 20 C. or by treatment with Water at Bil-90 C. It can thereafter undergo the after-treatment usual for viscose yarns. The dry tenacity of the thread is 1.7 g./denier, the wet tenacity 1.2 g./denier, the elongation at rupture is 28% when dry and elongation at rupture is 43% when wet. The filaments are of substantially round cross-section.

Example I! 330 kg. of cotton linters having a degree of polymerisation of 750 are converted to alkali cellulose by treatment with caustic soda, the product containing 30% cellulose and 15% caustic soda and having a degree of polymerisation of 450. This alkali cellulose is xanthogenated with 45% of carbon disulphide for 3 hours. The product is powdered and malaxated on rolls with 1112 kg. of 3% aqueous caustic soda, the temperature being maintained at 2 C., and the material being passed 10 times between the rollers set at 5 mm. distance apart. 210 kg. of water is then added and the malaxation continued for 2 hours in a Bandbury mixer at 0 C. There is then obtained a Xanthogel containing 7.8% caustic soda and 13% cellulose, having a viscosity of 2500 poises. This xanthogel is dry-spun under a pressure of 15 kg./sq. cm. at the spinnerets into air at room temperature and the filaments immediately become non-sticky. The product obtained under the same spinning conditions as in the previous example contains filaments of 0.45 denier having comparable physical properties.

I claim:

1. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose Xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 1900 poises, a cellulose content of at least and a caustic soda content of 3-10? the volume of the dispersing phase being insufficicnt to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the celluose in the products.

2. Process for the production of filaments and similar products from cellulose xanthogenate, which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 1000 poises, a cellulose content of at least 10% and a caustic soda content of 3-10 the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products by treatment with cold dilute acid.

3. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 1000 poises, a cellulose content of at least 10% and a caustic soda content of 3-10%, the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products by treatment with hot aqueous liquid of pH at least 7.

4. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda. which dispersion has a viscosity of at least 2000 poises, a cellulose content of at least 10% and a caustic soda content of 3-10%, the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products.

5. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 1000 poises, a cellulose content of 20-25% and a caustic soda content of 3-10%, the volume of the dispersing phase being insuflicient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products.

6. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 2000 poises, a cellulose content of 20-25% and a caustic soda content of 3-10%, the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products.

7. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda which has a viscosity of at least 2000 poises, a cellulose content of at least and a caustic soda content of 3-10%, the volume of the dispersing phase being insufiicient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products while stretching the products further during such regeneration treatment.

8. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 2000 poises, a cellulose content of -25% and a caustic soda content of 13-10%, the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products continuously with their production and thereafter regenerating the cellulose in the products while stretching the 6 production further during such regeneration treatment.

9. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a. spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 2000 poises, a cellulose content of at least 10% and a caustic soda content of 3-10%, the volume of the dispersing phase being insufficient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products by 5001000% continuously with their production and thereafter regenerating the cellulose in the products.

10. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 2000 poises, a cellulose content of 20-25 and a caustic soda content of 3-10%, the volume of the dispersing phase being insufiicient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products by 500-1000% continuously with their production and thereafter regenerating the cellulose in the products.

11. Process for the production of filaments and similar products from cellulose xanthogenate which comprises extruding through a spinneret into. air at room temperature a dispersion of cellulose xanthogenate in aqueous caustic soda, which dispersion has a viscosity of at least 2000 poises, a cellulose content of 20-25% and a caustic soda content of 310%, the volume of the dispersing phase being insufiicient to produce total hydration of the molecules and the degree of hydration of the molecules being substantially uniform, stretching the products by 5001000% continuously with their production and thereafter regenerating the cellulose in the products while stretching the products further during such regeneration treatment.

NICOLAS DRISCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,357,206 Fuller Oct. 26, 1920 2,036,752 Herzog et a1. Apr. 7, 1936 2,284,028 Ubbelohde May 26, 1942 FOREIGN PATENTS Number Country Date 321,679 Great Britain Nov. 11, 1929 

1. PROCESS FOR THE PRODUCTION OF FILAMENTS AND SIMILAR PRODUCTS FROM CELLULOSE XANTHOGENATE WHICH COMPRISES EXTRUDING THROUGH A SPINNERET INTO AIR AT ROOM TEMPERATURE A DISPERSION OF CELLULOSE XANTHOGENATE IN AQUEOUS CAUSTIC SODA, WHICH DISPERSION HAS A VISCOSITY OF AT LEAST 1000 POISES, A CELLULOSE CONTENT OF AT LEAST 6% AND A CAUSTIC SODA CONTENT OF 3-10%, THE VOLUME OF THE DISPERSING PHASE BEING INSUFFICIENT TO PRODUCE TOTAL HYDRATION OF THE MOLECULES AND THE DEGREE OF HYDRATION OF THE MOLECULES BEING SUBSTANTIALLY UNIFORM, STRETCHING THE PRODUCTS CONTINUOUSLY WITH THEIR PRODUCTION AND THEREAFTER REGENERATING THE CELLULOSE IN THE PRODUCTS. 